Uranium isotope fractionation during adsorption, (co) precipitation, and biotic reduction
Uranium contamination of surface environments is a problem associated with both U-ore extraction/processing and situations in which groundwater comes into contact with geological formations high in uranium. Apart from the environmental concerns about U contamination, its accumulation and isotope composition have been used in marine sediments as a paleoproxy of the Earth’s oxygenation history. Understanding U isotope geochemistry is then essential either to develop sustainable remediation procedures as well as for use in paleotracer applications. We report on parameters controlling U immobilization and U isotope fractionation by adsorption onto Mn/Fe oxides, precipitation with phosphate, and biotic reduction. The light U isotope (235U) is preferentially adsorbed on Mn/Fe oxides in an oxic system. When adsorbed onto Mn/Fe oxides, dissolved organic carbon and carbonate are the most efficient ligands limiting U binding resulting in slight differences in U isotope composition (δ238U = 0.22 ± 0.06‰) compared to the DOC/DIC-free configuration (δ238U = 0.39 ± 0.04‰). Uranium precipitation with phosphate does not induce isotope fractionation. In contrast, during U biotic reduction, the heavy U isotope (238U) is accumulated in reduced species (δ238U up to −1‰). The different trends of U isotope fractionation in oxic and anoxic environments makes its isotope composition a useful tracer for both environmental and paleogeochemical applications.
2016
2019-10-04 08:38:38
1033
Uranium, fractionation, biotic, abiotic, oxides
r6
Duc Huy
Dang
70
Breda
Novotnik
70
Wei
Wang
70
Bastian R.
Georg
70
Douglas R.
Evans
70
COBISS_ID
3
5458427
DOI
15
10.1021/acs.est.6b01459
NUK URN
18
URN:SI:UNG:REP:RFKQHTTM
Dang_2016.pdf
4504804
Predstavitvena datoteka
2019-10-04 08:39:02
0
Izvorni URL
2019-10-04 08:38:49